A captive adult common mynah (Acridotheres tristis) died shortly after a course of seizure and opisthotonous with an illness characterized by severe lethargy, depression, loss of appetite, polyurate, and urate discoloration. Abdominal distention and hepatomegly, visible over the abdominal skin, were noticed clinically. At necropsy, severe enlargement of liver with general discoloration was obvious. Histopathological findings included schizonts and gametes in the intestine, especially in the duodenum. Cytology from impression smears revealed intracyto-plasmic Atoxoplasma-like zoites in the inflammatory cells especially macrophages within the liver and in the contact smears prepared from the liver, lung, and spleen. Based on postmortem findings of the organisms in blood mononuclear cells and in impression smears of liver and Giemsa stained impression smears of liver, the spleen and lung atoxoplasmosis caused by Isoapora sp. was specified as the cause of death. According to the literature, visceral coccidiosis (atoxo-plasmosis), described here, could be considered as one of the severe causes of mortality among captive birds.